Sen. Barack Obama’s visit to a Boca Raton synagogue Thursday was his latest in a series of efforts to convince a skeptical American Jewish community that he is a true supporter of Israel.

Obama, who spoke at Florida’s B’nai Torah Congregation, has been dogged by questions of how his foreign policy views would affect the Jewish state. There is concern that he would foster direct negotiations with Iranian President Mahmoud Ahmadinejad, who has called for the destruction of Israel. Obama's also been dealing with erroneous suggestions and suspicions that he is Muslim or anti-Israel.

The controversy has been picked up by many Republicans — including President Bush, who hinted at Obama in a speech to the Israeli parliament last week, chastising leaders who want to negotiate with terrorists, calling it the “false comfort of appeasement.”

The Obama campaign has been facing similar attacks for months, centered around his proposal to meet with Ahmadinejad in his first year in office.

“There is an orchestrated effort to mischaracterize and falsely present his views and things about him personally,” said one Obama aide.

Obama's synagogue visit
Obama hit the issue head-on in his remarks at the synagogue. "People have been getting e-mails nonstop," Obama said. "I have said throughout this campaign that we should not negotiate with Hamas or Hezbollah, and that’s why I reject the attempts by some of my opponents in this campaign to distort my position. They are counting on fear, because they know they haven’t told the truth.”

Jewish Democratic congressmen and other community leaders acknowledge there is a nervousness about Obama that could hurt him on Election Day.

Video: Obama and the Jewish vote
“I have, over the last six months, been bombarded with this stuff,” said Ira Forman, the executive director of the National Democratic Jewish Council. “I live in a world where the people I talk to are very involved in the Jewish community, and where this issue is most intense is in the inner circle.”

It is not an unprecedented tactic. Howard Dean, who sought the Democratic nomination in 2004, was pegged as anti-Israel in an anonymous e-mail campaign after he referred to Hamas members as “soldiers” and said he would favor an “even-handed” Middle East policy, a term many Jews equate with support for Palestinians over Israelis.

Jewish leaders say that once these characterizations enter the public lexicon — whether true or not — they are hard to fight.

Matt Dorf, a Democratic strategist who served as an adviser to Dean’s campaign, said Jewish Democrats have learned a lot of lessons from 2004, both from Dean's experience and the broader “Swift Boat” attacks that nominee Sen. John Kerry faced about his time during the Vietnam War.

“An aggressive and timely response is needed,” said Dorf, who now advises Dean as chairman of the Democratic National Committee. “And that is something the campaign has done very, very well.”

Campaign praiseIndeed, many Jewish leaders praised Obama’s reactions to Bush’s comments last week. They say it will need to be followed with large forums to Jewish audiences and small-group conversations with Jewish leaders.

Jews make up less than 2 percent of the American electorate, but are seen as an important constituency. Why? Because they are politically active and vote in large numbers in several important swing states, including Florida, where Jews make up 3.6 percent of the population.

While Jews were once a consistently Democratic voting bloc, more have been embracing Republican candidates in recent years. Bush received 24 percent of the Jewish vote in 2004, the largest percentage for a Republican in 20 years.

Jewish voters do not choose candidates on the Israel issue alone, and are often seen as a liberal group on social issues like abortion and health care. But Middle East policy is a litmus test for many, who will not support a candidate they believe will threaten the viability of the Jewish state.

Many Jews are being bombarded with information about Obama, both from anonymous e-mails and by campaigns orchestrated by various organizations. False rumors that he is Muslim have been swirling for months, and some Jews are concerned about his relationship with the Rev. Jeremiah Wright, who has made anti-Israel comments.

Some Jewish Republicans are trying to make the case against Obama, suggesting he has called for a summit of Muslim nations and is aligned with advisers who placed blame on Jews for the breakdown of the Middle East peace process.

The Republican Jewish Coalition ran ads in several Florida newspapers Thursday, saying Obama’s “dangerously naïve policies and lack of experience raise real concerns for all Americans, especially those who care about Israel and the future of the Jewish people.”

“I’m not saying he supports Hamas, or Louis Farrakhan or Jimmy Carter,” said Matt Brooks, the RJC’s executive director. “But it begs the question: Why are all these people so comfortable supporting him?”

Reaching outObama has countered thus far by holding interviews with prominent Jewish journalists and speeches to Jewish audiences. Already, several rabbis said they receive frequent updates from the Obama campaign. He is expected to address the American Israel Public Affairs Committee next month.

Obama has also been answering questions about his ties to Nation of Islam leader Louis Farrakhan, who has called Judaism a "gutter religion."

Video: Help Obama doesn’t need
"I have some of the strongest support from the Jewish community in my hometown of Chicago and in this presidential campaign," Obama said at an NBC debate in February. "And the reason is because I have been a stalwart friend of Israel's. I think they are one of our most important allies in the region, and I think that their security is sacrosanct, and that the United States is in a special relationship with them, as is true with my relationship with the Jewish community."

The Obama campaign aide said he believes a vast majority of American Jews are not believing what they hear from their neighbors or learn on the Internet.

“We’re not finding it a challenge, when presented with the facts, to get people to feel comfortable with what his position is,” the aide said. “The challenge is every day the opposition sends out a new attack, and anything that isn’t challenged has the potential to be believed.”

Dorf said the questions about Obama’s Middle East views have not been fully explained yet because he is still largely focused on the primary campaign, and has been competing mostly in states without sizeable Jewish communities. Thursday marked his first campaign appearance in Florida, a state that was punished and stripped of delegates for moving its primary date forward.

Video: Todd's First Read
“I’m not sure the genie is out of the bottle,” Dorf said. “He has been attacked, he’s answered it in a timely way, and the more people get to know him and he has the full efforts of a general campaign, people will see he is the person he is.”

A recent Gallup analysis of tracking polls found Obama would garner 61 percent of American Jewish support in a race against Sen. John McCain, while Sen. Hillary Clinton would win 66 percent in a similar match-up.

Where his rivals stand
McCain has a strong track record on Israel and has been a leading supporter of the Iraq war, which originally garnered strong support among Israel advocates. Clinton also has won plaudits from the Jewish community, but was criticized for embracing the wife of the late Palestinian Authority president Yasser Arafat when she was first lady.

Both Clinton and Obama fare worse than previous Democratic candidates because McCain is seen as strong on Israel and more moderate on social issues than other Republican candidates. Democrats said an important part of their plan will be to characterize McCain as a social conservative and as an extension of the Bush presidency.

But, Forman said, it will be nearly impossible to win over all of those who say they would support Clinton but choose McCain over Obama.

"I think some of that is gone,” he said. “It's not because we can't make a good argument. I just think that these attacks appeal to emotions and not facts.”

NBC News and National Journal reporter Adam Aigner-Treworgy contributed to this report.